The present invention relates to the endless tracks for track-type tractors and particularly to methods and apparatus for prolonging the life of the components of such tracks.
The tracks of a track-type tractor are generally subjected to a very high rate of wear because of the abrasive atmosphere in which they normally operate. Numerous improvements in such tracks have been made over the years in order to prolong the life thereof. However, certain components within the track are still subjected to very high rates of wear.
Perhaps the most critical components of the many components making up the drive system of such a crawler tractor are the drive surfaces of the traction chain bushing and sprockets. These components are normally subjected to a very high wear rate because of the high loading on these components. This high rate of wear must be compensated for in order to avoid a mismatch of operating pitch between the chain and sprocket which could subject the components to increasingly high load stresses and scrubbing of pins and bushings and result in a premature wear and failure of the entire track chain.
Improvements in internal sealing and lubrication of the track chain joints have limited most wear in the track chain to the external bushing surfaces. When one side of the track bushing becomes worn, the bushing can be rotated 180.degree. to permit the other side to be worn before the track bushing is discarded. Track pin pushings have been constructed to have an oval-shaped wear surface to increase the service life of the bushing. Such bushings are the subject of U.S. Pat. No. 3,313,578. Other patents of interest in connection with chain and sprocket wear problems are as follows: U.S. Pat. No. 3,220,273 issued Nov. 30, 1965; U.S. Pat. No. 1,358,474 issued Nov. 9, 1920; and U.S. Pat. No. 1,193,550 issued Aug. 8, 1916. British specification No. 28,981 dated A. D. 1897 also discloses an adjustable pitch chain which may be considered of interest with regard to the subject invention.